Switching devices are already known from the prior art such as touch switches, rocker switches, pressure switches or pull switches which have defined on and off switching states. An electric displacement drive which is to be switched by a switch of this kind consequently knows only two switching states: switched on and switched off.
An exception to this is the rotary switch and sliding switch with integrated potentiometer. With defined end positions of the potentiometer or rotary switch which correspond to the end positions of an object to be displaced a normally linear area is formed between the end positions where a signal clearly determined by the position of the rotary switch is issued by the rotary switch. Absolute positions of the object being displaced are thereby allocated to the potentiometer values. It is thereby possible for example when adjusting a window pane by means of an electric window winder drive to set and preselect intermediate positions of the window pane.
Known rotary switches with integrated potentiometer do not allow however a control over the displacement, more particularly the dynamic characteristic values of the displacement of an object being displaced, from each and every switch position. More particularly it is not possible to control the displacement speed and fine adjustment of the displacement. Also the possibility of controlling the displacement speed of an adjustment would considerably increase the general operating comfort.
A switching device according to the preamble of claim 1 is known from European Patent EP A 0 324 291. This relates to an ideal value transmitter for controlling the position of an object with an endlessly rotatable control button which during rotation of the control button produces impulses whose number is proportional to the turning angle of the button. An ideal value relating to the position of the object to be controlled is detected from the number of impulses received, the position of the object to be controlled and the direction of movement. The number of impulses received is thereby calculated from the ratio between the turning angle of a displacement undertaken and the maximum angle accessible for an operator so that the impulses produced code the path which the object to be controlled is to run through starting from the starting position.
French Patent FR A 2 484 168 describes an electrical switching device for a window winder device with an operating element which can swivel in both directions and which depending on the swivel direction causes a closing or opening of a window pane. It is thereby proposed that with a short activation of the operating element the window pane is displaced at high speed. With a long activation of the operating element the window pane is displaced at a slower speed. Corresponding current circuits are provided for this.
German Patent DE 44 04 594 A1 discloses an operating device for steering, accelerating or braking a motor vehicle with an operating element which has a defined neutral position and starting from the neutral position can be displaced in two deflection directions. An adjustment of the steering, of the engine or braking system of the motor vehicle is carried out in dependence on the degree of deflection of the operating element from its rest position or in dependence on the time length of the deflection of the operating element.
From German Patent DE 35 32 575 A1 an electric switch is known for a drive motor with an operating slider. The operating slider is in active connection with a sliding resistance as well as an associated control electronics so that the sliding path of the operating slider is directly proportional to the displacement path of a sliding roof, window or the like.
German Patent DE 37 36 400 A1 discloses a safety device for movable parts, more particularly for window winders and sliding roofs of motor vehicles. A movable part such as a window pane is moved into a closed position by means of a drive motor over a dangerous clamping area where foreign bodies can be clamped between the movable part and a resting part. The displacement speed is thereby reduced in the dangerous clamping area during closing of the movable part.